The present invention relates to a tank for storing gas at high pressure, the tank comprising a confinement volume in selective communication with the outside via coupling means. More particularly, the invention relates to tanks that are lightweight and compact for storing gas at high pressure in applications to non-polluting terrestrial vehicles (LNG, H2, LPG, . . . ) or indeed to aircraft or spacecraft.
Conventional tanks for storing gas at high pressure are known generally to be in the form of cylinders or spheres. Those types of tank used singly or on a rack, occupy a large amount of volume because of their shape and because of the presence of projecting means for coupling and for providing the protection required by regulations (against impact, fire, . . . ). Combining cylinders does indeed serve to reduce one of the dimensions used for storage, for example the height dimension, but it inevitably gives rise to storage assemblies that are heavy and expensive, and that are larger in size with respect to their other dimensions. In the best known prior art configurations, the volume dedicated to storing gas does not exceed 40% of the overall volume for a maximum structural ratio of 1.5 liters per kilogram (1/kg).
The present invention seeks to remedy the above-mentioned drawbacks of the prior art, and in particular to provide a tank for storing gas at high pressure which presents reduced size and mass when storing a volume equivalent to that of a conventional tank, while nevertheless complying with the protection conditions required in the prior art.
These objects are achieved by a tank for storing gas at high pressure, the tank comprising a confinement volume in selective communication with the outside via coupling means, wherein said confinement volume comprises a duct of oblong section formed by elongate first and second portions interconnected by curvilinear third and fourth portions, and wherein said duct is disposed as a plurality of touching segments so as to enable at least one of the elongate portions of one touching segment to bear against a corresponding one of the elongate portions of an adjacent touching segment in said plurality of touching segments.
The invention thus proposes a tank for storing gas at high pressure which enables mass and bulk to be reduced significantly compared with prior art tanks for given storage volume. Furthermore, the tank of the invention is of a design which not only optimizes the tank in terms of mass and bulk, but also guarantees that it complies with the safety requirements for this type of storage.
The duct may have a section of varying dimensions.
In particular embodiments, the third and fourth curvilinear portions are semicircles.
More specifically, the elongate portions are substantially rectilinear.
In an embodiment of the invention, the duct is disposed as a spiral coil about an axis ZZxe2x80x2 from an inner end of said duct having the coupling means to a closed outer end finishing off said duct.
In this way, the coupling means of a tank no longer project therefrom, thus reducing the overall size thereof.
The tank may be in the form of a wheel, it may be oval in shape, or indeed it may be rectangular in shape.
According to a particular feature of the invention, the said tank defines front walls that are substantially plane and parallel.
Alternatively, the tank defines at least one front wall that is substantially frustoconical.
According to a particular characteristic of the invention, an inner surface of the tank defined by the coiled duct includes an internal hoop.
The innermost turn of the coil whose inside face cannot benefit from an adjacent turn compensating the force exerted by the gas pressure is thus reinforced on the inside.
According to another characteristic of the invention, an outer surface of the tank defined by the coiled duct includes an outer hoop.
The outermost turn of the coil whose outside face cannot benefit from an adjacent turn compensating the force exerted by the gas pressure is thus reinforced on the outside.
The design of a tank of the invention can also be optimized by being disposed as a coil of helical type.
Thus, in an embodiment of the invention, the duct is disposed as a helical coil about an axis ZZxe2x80x2 starting from a closed first end and extending to a second end having the coupling means.
The design of a tank of the invention can also be optimized by disposing the duct in a zigzag configuration serving in particular to make a tank in the form of a rectangular parallelepiped.
Thus, in another embodiment of the invention, the duct is disposed in a zigzag configuration from a first end having the coupling means to a second end which can be closed or which can likewise have coupling means.
According to a particular feature, the tank has bends in which at least one bead of welding is formed.
The tank may also comprise a winding surrounding the sides of the zigzag formed by the duct.
The present invention also provides a method of manufacturing a tank for storing gas at high pressure, the method comprising the following steps: curving a duct of oblong section into a plurality of touching segments so as to enable at least one elongate portion of a touching segment of said duct to bear against an elongate portion of an adjacent touching segment; heat-treating said duct while it is temporarily banded; and winding a carbon or glass fiber over the outside surface of the duct.
The invention thus provides a method of manufacturing a tank which makes it possible to obtain a tank that is at least as reliable in terms of safety as tanks known in the prior art and which provides significant savings in mass and bulk.
According to a feature of the invention, the method further comprises a step of closing a first end of said duct and a step of fixing communication means to a second end of said duct.
According to a particular characteristic, the method comprises a step of forming said duct of oblong section by means of a metal strip that is closed by axial welding.
According to another feature of the invention, the operation of curving the duct further comprises applying pressure inside said duct and/or preheating said duct.
In an implementation of the invention, the curving step corresponds to coiling the duct about an axis ZZxe2x80x2, and the method further comprises a step of inserting an inside hoop against the inner surface defined by said coil.
In another implementation of the invention, the curving step corresponds to folding the duct into a zigzag configuration, and the method also comprises a step of welding the bends of the duct in the zigzag configuration.
Specifically, the method of the invention further comprises a step of tightening the external winding.
Advantageously, the method further comprises a step of wrapping the tank in glass fiber winding.